Pulse stretching circuit



Aug. 22, 1950 c. A. MIZEN PULSE STRETCHING CIRCUIT Filed April 50, 1946 mutij lNl/E/VTOR. CARLTON A. MiZEN Z) /L&?.

A T TORNE Y Patented Aug. 22, 1950 PULSE STRETCHING CIRCUIT.

(3arlton1A.. Mi zen,. Cambridge;z.Mass:, .assignon to Unitedv Statesiof Americaeaserepresented-by -thee;

Secretary. of War- Application-Aprii 30, 1946; Serial No: 666,003

4 Claims. 1.

Thi's' in-venti'on relates to electric'al circuits: and more particularly to: pulse conversion circuits.

In certain applieationsutis' desirable to convert pulses. of radio"frequency energy'into other pulses h aveza constant Width and which-have an amplitudepropcrtional to the aznpli'tude of the original puises'.

Previous circuitshaVe-been designed which have 'tunctioned 'satisfac torilyonly as pulse stretchers -o1 "1'3uls'e=1engtiie-ners"and-have operated: to prod uce a-pulse expanded'tosome constant width from: the input-=- pulse: However; such pulse lengtheners have, not produced output pulses which wermproportirbnal in. amplitude to that of the input-pulses. This difiiculty is most pro:- nounced whenappreciabl voltage or power is re- 'qui'r ed ofi' the output pulsewave;

Accordingly, an object of the present'invention 'is t'o produce a" pulse conversiomcircuit which is adapted to produce output pulses' of constant *w-i'dth and of" amplitudeproportional to the amplituder of pulses applied to its input.

' A further: object of the-invention is t0-*pr0- duceesuch apul-seconversion circuit capable of considerable-voltage or 'power inthe outputipirlses.

Other. objects and i advantages of" the invention will be apparent during the course of the following dseription.

' In one ernbodim entof the-invention the -input pulsesare applied 'ztoa-standard constant-widthpulse generator (here-a blocking oscillator type pulse generator). The output cfthi-s-pulse gencrater is: a negative constant-width-pulse which is applied across the grid and cathode of a vacuum tube. A:capacitance'is'connected in series with the externa1 cathode circuit of this vacuum tube; thiscapacitance bein electricallyconnected through a unilateral impedance (in this case, a diode) aczosssthe: inpuhpulse source; hence, the voltage. across this capacitance when the vacuum tube isnon-conducting willbe proportional to. the amplitude. of the input pulses... The negativeconstant' width-pulse drives the gridhighly; negative, isolating the cathode and permitting the capacitance to charge through the diode to some negative voltage proportional to the amplitude of the input pulses. The negative output pulses are taken off across the capacitance. The vacuum tube is conducting during the final portion of its duty cycle to provide discharge of the capacitance, the grid of the tube being made positive by the positive tail of the applied pulse.

In the accompanying drawing, forming a part of this specification, the single figure shows a signpliiied:.combined block-and+schematie diagram .of

one embodiment. of this invention.

In the figure the lines fromth'eeblocks. of the 'diagrarrr represent the-high! voltage sides; of f the electrical connections, the remaining lines being at:- ground potential Imthe-'-.figure;v numeral lfirzdesignatesan input terminal .atxwhich point the input pulsesiare ape plieds. The" input: .pulsesare applied to- .a differ.- entiating circuit II which produceszaisharpdifferentiated pulse. A D. C..restorer% IZifi'Xes. the quiescent level of 1 the output of diiferentiating circuit. and: clips the positive portion. of the differentiated pulses. Theresultant pulsesyare applied: to a. limiter circuit l3 which produces 131111595201: uniform amplitude. Theseuniform-amplitude:pulsesstrigger; a pulse-forming circuit l4 Which-produces.pulses: of constant width and of constant amplitude. These-*constant-width, con.- stanteamplitude pulses. are appi-iedto the grid of a. vacuum tube l5 which is maintained quiescently ima nonrconducting.condition. The plate and the-.grid of tube. I5..are maintainedata negative potential a. power supply. l 1, a suitable voltage being, about 40 .volts negative. A suitable block, ing biasonlthe grid. of tube [5 is obtained over resistance. It. Numeral. l8. designates-a by-pass condenser. for anode voltage; supply 11.

In. seriesuwith .the. external cathode circuit. of tube. l5 is a. capacitance. l9 whichis: connected through. a diodeZB to the. output of differentiating, circuit I]... Diode- 29 serves as a unilateral impedance and makes the voltage on.=capa.citance l9, whentube I5. is, non-conductingafunction oithe amplitude. oflthedifferentiated pulses of differentiating circuit. II. and. hence. a. function oijtlieamplitudeof thein-put pulses at inputterminalj'l o..

The. operation of the circuitis as. follows:.

The tub e. I5? is customarily. in. a non-. conducting condition. At theinceptionof the. negativepulse fromthe. pulse-forming. circuit M, the. grid. of tube I51. is. driven. sharply negative, thus-1 causingno change in. tube. conductivity. During;the pulse the Voltage across capacitance is is negative with respect to ground and of an amplitude proportional to the amplitude of the input pulses at input terminal in. The output pulses are then of constant width and of amplitude proportional to the amplitude of the input pulses and are taken off across output terminals 2 I. The positive tail of the applied pulse drives the grid of tube 15 positive and causes the tube to conduct, thus discharging capacitance I9.

I? Will be obvious that the circuit, as shown 3 in the figure, has been practically reduced to the minimum number of components and would be completely reduced to the minimum number of components if the limiter l3 were removed.

Accordingly, it is obvious that various improvements, additions and modifications may be made to the circuit. For example, a number of ordinary pulse amplifiers may be inserted between the pulse input 1! and the difierentiating circuit H. The limiter stage I 3 may be eliminated, if desired, but its inclusion generally gives more satisfactory operation and prevents spurious triggering of the pulse-forming circuit I l. The pulseforming circuit M has not been specified since a wide variety of equivalents are possible (e. g. a blocking oscillator, a delay multivibrator, or a delay line oscillator). Low impedance sources, such as cathode followers, may be inserted in the customary manner at various points in the circuit to prevent pulse distortion due to loading effects. Thus, a cathode follower may be, and generally is, inserted between the pulse-forming circuit l4 and the grid of tube l5.

It will be obvious that there may be deviations from the invention as described which still fall fairly within the spirit and scope of the invention.

Accordingly all such deviations are claimed whichfall fairly within the spirit and scope of the invention as identified in the hereinafter appended claims.

What is claimed is:

1. A pulse conversion circuit comprising an electron discharge tube having at least anode and cathode electrodes, a capacitor, a point of fixed potential, said capacitor being electrically con- 1' nected between said cathode and said point of fixed potential, bias means connected between said point of fixed potential and said anode to maintain the impedance of said electron discharge tube normally high, means including a unilateral impedance forming a path for signal pulses of predetermined polarity in series with said capacitor for charging thereof to a potential determined by the amplitude of said signal pulses, means keyed by said signal pulses to generate negative-going pulses of constant duration and having trailing edges which are positive with respect to the leading edges, means responsive to said trailing edges to lower the impedance of said electron discharge tube sufiiciently to quickly discharge said capacitor connected to said bias means, and an output circuit connected across said capacitor.

2. A pulse conversion circuit comprising an electron discharge tube having at least anode, cathode and grid electrodes, a source of negative bias potential connected to said anode, a capacitor connected between said cathode and said source, a resistor connecting said anode and grid, a source of pulse signals of a predetermined polarity, means, connected to said grids, responsive to said pulse signals to generate pulses having constant duration and having trailing edges which are positive with respect to the leading edges,

means to impress said pulses upon said grid electrode, the potential of said trailing edges rising to an extent sufiicient to overcome said negative bias potential and render said tube conducting, a circuit including a diode disposed in series with said capacitor and said pulse source for impressing said signal pulses upon said capacitor to charge it to a potential determined by said pulse signal amplitude, said capacitor retaining said charge until said electron discharge tube is made conducting, and an output circuit connected across said capacitor.

3. A pulse conversion circuit comprising a differentiating circuit, means to impress a signal pulse of predetermined polarity upon the input of said differentiating circuit, a D. C. restorer and a limiting amplifier connected to the output of said difierentiating circuit, a pulse generator keyed by the output of said amplifier for producing pulses of constant duration, an electron discharge tube having at least anode and cathode electrodes, a point of fixed potential, bias means negative with reference to said point of fixed potential and connected to said anode to maintain said tube normally blocked, a capacitor connected between said cathode and said point of fixed otential, a unilateral impedance connected between the output of said differentiating circuit and the junction of said cathode and condenser whereby the said condenser is charged to a potential determined by the amplitude of each signal pulse, means disposed intermediate said generator and said discharge tube responsive to the trailing edge of the pulses in the output of said pulse generator to render said electron discharge tube conducting and effect a discharge of said capacitor, and an output circuit connected across said capacitor.

4. A conversion network for spaced pulses, comprising a condenser, an electron discharge tube circuit in series with said condenser for controlling the discharge thereof, means normally blocking said discharge tube circuit, unidirectionally conducting means forming a path for said pulses to said condenser to permit charging thereof, separate circuit means including a pulse generator for producing, in response to the application of said pulses thereto, output pulses having constant duration, means for applying said output pulses to said discharge circuit and said blocking means to render said blocking means ineffective and discharge said condenser, and an output circuit for said condenser.

CARLTON A. MIZEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,399,135 Miller et al Apr. 23, 1946 2,419,350 Easton Apr. 2 1947 2,439,321 Starr Apr. 6, 1948 

